1. Technical Field
The present invention relates to a light diffusion plate and a backlight module using the same and, particularly, to a light diffusion plate and a backlight module using the same employed in a liquid crystal display.
2. Description of the Related Art
Referring to FIGS. 12 and 13, a typical direct type backlight module 100 includes a frame 110, a plurality of light sources 120, a light diffusion plate 130, and a typical prism sheet 140. The light sources 120 are positioned in an inner side of the frame 110. The light diffusion plate 130 and the typical prism sheet 140 are positioned on the light sources 120 above a top of the frame 110. The light diffusion plate 130 includes a plurality of diffusing particles (not shown) configured for diffusing light. The typical prism sheet 140 includes a transparent substrate 141 and a prism layer 143 formed on a surface of the transparent substrate 141. A plurality of elongated V-shaped ridges 145 is formed on the prism layer 143.
In use, light emitted from the light sources 120 enters the diffusion plate 130 and becomes scattered. The scattered light leaves the diffusion plate 130, travels through the typical prism sheet 140, and refracts out at the elongated V-shaped ridges 145.
The refracted light leaving the typical prism sheet 140 is concentrated at the prism layer 143, increasing the brightness of the prism sheet 140. The refracted light propagates into a liquid crystal display panel (not shown) positioned above the prism sheet 140.
However, although light from the light sources 120 enters the diffusion plate 130 and becomes scattered, the light leaves the prism sheet 140, and forms strong light spots.
In order to reduce or eliminate the strong light spots, the backlight module 100 should further include an upper light diffusion film 150 positioned on the prism sheet 140.
However, although the upper light diffusion film 150 and the typical prism sheet 140 contact each other, a plurality of air pockets exist around the boundaries of the light diffusion film 150 and the typical prism sheet 140. When light passes through the air pockets, some of the light undergoes total reflection along one or more corresponding boundaries. The upper light diffusion film 150 may absorb a certain amount of the light from the prism sheet 140. As a result, a brightness of light illumination of the backlight module 100 is reduced. In addition, the matrix of the elongated V-shaped ridges 145 is substantially the same as the pixel matrix of the panel, fringes of Morie Interference often appears on the panel, and the display effect is affected.
Therefore, a new diffusion plate and a new backlight module are desired to overcome the above-described shortcomings.